My Triton T80i shut down whilst in use?

Whilst standing under the T80i shower I detected it momentarily going cooler, then shutting down altogether. The 'Red' pressure sensor flag has appeared in the window. The water flow (mains pressure) is OK. I now have the unit off the wall, all the electrics look fine, the incoming solenoid is OK electrically, but looks a bit manky. Is there a blocked filter somewhere on the input side? If I look into the Water Inlet (short nylon stub), there is no filter as such - just a seive-like gauze at the bottom of the tube in the nylon material itself - and it appears clean/clear..